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Mathematics

Prove the following identity:

(1+tan2A)+(1+cot2A)=(1sin2Asin4A)(1 + \tan^2 A) + (1 + \cot^2 A) = \Big(\dfrac{1}{\sin^2 A - \sin^4 A}\Big)

Trigonometric Identities

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Answer

Solving L.H.S. of the equation :

(1+tan2A)+(1+cot2A)sec2A+cosec2A1cos2A+1sin2Asin2A+cos2Acos2Asin2A1cos2Asin2A1(1sin2A)sin2A1sin2Asin4A.\Rightarrow (1 + \tan^2 A) + (1 + \cot^2 A) \\[1em] \Rightarrow \sec^2 A + \cosec^2 A \\[1em] \Rightarrow \dfrac{1}{\cos^2 A} + \dfrac{1}{\sin^2 A} \\[1em] \Rightarrow \dfrac{\sin^2 A + \cos^2 A}{\cos^2 A \sin^2 A} \\[1em] \Rightarrow \dfrac{1}{\cos^2 A \sin^2 A} \\[1em] \Rightarrow \dfrac{1}{(1 - \sin^2 A) \sin^2 A} \\[1em] \Rightarrow \dfrac{1}{\sin^2 A - \sin^4 A} .

Since, L.H.S. = R.H.S.

Hence, proved that (1+tan2A)+(1+cot2A)=(1sin2Asin4A)(1 + \tan^2 A) + (1 + \cot^2 A) = \Big(\dfrac{1}{\sin^2 A - \sin^4 A}\Big).

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